Biological activity in Cerrado soils: evaluation of vegetation, fire and seasonality effects using the “bait-lamina test”

Aims The Cerrado, a South American savanna, is con- sidered a priority for conservation. In this case study, we assessed soil feeding activity as a way to improve un- derstanding of the ecosystem functioning, in order to support and refine conservation strategies. Methods Soil feeding activity was assessed using the bait-lamina method under different environmental con- ditions: in the dry and rainy seasons, in burned and unburned areas, and under native and invasive grasses. Results Feeding activity was significantly reduced after fire, but recovered to pre-fire levels with the rains. Activity increased significantly during the rainy season in both areas, being more pronounced in the unburned area. The highest feeding activity was observed under the invasive grass (Melinis minutiflora). Feeding activ- ity declined with soil depth and was affected by season and fire. Conclusions Seasonality was the most important factor affecting the feeding activity of soil organisms, followed by the fire history and the extant vegetation. Although this method does not allowdistinguishing between feed- ing activity of different organisms, it can provide valu- able insights into differences in soil functioning due to changes in environmental conditions

The inflorescences structure of Cyperus L. section Luzuloidei Kunth (Cyperaceae)

In the present work the inflorescences of 12 species of Cyperus sect. Luzuloidei Kunth sensu Kükenthal were analyzed using the methodology and terminology of Troll's school. All the inflorescences studied are polytelic (indeterminate). The inflorescences are anthela-like or capitate, and can be terminal or pseudolateral. Below the main florescence a paracladial zone is present. In this zone three types of branching were observed, i.e. normal, accessory-axillar and prophyllar branching, whose position vary among the different species. In the paracladial zone a subzone of long paracladia and a subzone of short paracladia were observed. In the short paracladial subzone the spikelets are clustered in fascicles, which can be serial, prophyllar or mixed. Variation in length and position of pherophylls, length of prophyll, number and degree of branching were noticed. The systematic value of the inflorescences in the section Luzuloidei is discussed.Fil: Guarise, Nicolas Javier. Universidad Nacional del Litoral; ArgentinaFil: Vegetti, Abelardo Carlos. Universidad Nacional del Litoral; Argentin

Potential impacts of climate change on biogeochemical functioning of Cerrado ecosystems

The Cerrado Domain comprises one of the most diverse savannas in the world and is undergoing a rapid loss of habitats due to changes in fire regimes and intense conversion of native areas to agriculture. We reviewed data on the biogeochemical functioning of Cerrado ecosystems and evaluated the potential impacts of regional climate changes. Variation in temperature extremes and in total amount of rainfall and altitude throughout the Cerrado determines marked differences in the composition of species. Cerrado ecosystems are controlled by interactions between water and nutrient availability. In general, nutrient cycles (N, P and base cations) are very conservative, while litter, microbial and plant biomass are important stocks. In terms of C cycling, root systems and especially the soil organic matter are the most important stocks. Typical cerrado ecosystems function as C sinks on an annual basis, although they work as source of C to the atmosphere close to the end of the dry season. Fire is an important factor altering stocks and fluxes of C and nutrients. Predicted changes in temperature, amount and distribution of precipitation vary according to Cerrado sub-regions with more marked changes in the northeastern part of the domain. Higher temperatures, decreases in rainfall with increase in length of the dry season could shift net ecosystem exchanges from C sink to source of C and might intensify burning, reducing nutrient stocks. Interactions between the heterogeneity in the composition and abundance of biological communities throughout the Cerrado Domain and current and future changes in land use make it difficult to project the impacts of future climate scenarios at different temporal and spatial scales and new modeling approaches are needed